This invention relates generally to hitches for making draft connections between vehicles, for example, between trailers and towing vehicles, and more specifically, to force responsive hitches.
Conventional trailer hitches generally include a support structure rigidly attached to the rear of a towing vehicle. A hitch ball connector is mounted to the rigid support structure and is engaged by a compatibly shaped receptacle or coupling mounted on the forward end of a tongue of the trailer frame. This creates a pivotal connection in a plane normal to the length of the towing vehicle but the connection is rigid along the lengths of the vehicles. Because of the longitudinal rigidity, longitudinal surges, both compressive and expansive, and vertical shocks, both up and down, are transmitted between the trailer and the towing vehicle.
Longitudinal surges and vertical shocks between the towing vehicle and the trailer have numerous sources. For example, upon acceleration or deceleration of the towing vehicle, expansive or compressive surges, respectively are longitudinally transmitted between the trailer and the towing vehicle. A driver commonly causes these surges when accelerating and decelerating the towing vehicle. Further, bumps, ruts, potholes, etc. in a road surface subject the towing vehicle and a trailer to vertical vibrations and other vertical shocks. These vertical shock forces are transferred between the towing vehicle and trailer through the trailer hitch. It is well known that undue wear and damage to the towing vehicle, the hitch, and the trailer result from continual surges and shocks commonly associated with towing a trailer. Thus, it is desirable to reduce effects on both the towing vehicle and trailer of the surges and shocks.
In addition to causing undue wear and damage to both the trailer hitch and the trailer, surges and shocks between the towing vehicle and its trailer can be detrimental to the cargo being hauled in the trailer. For example, live stock such as horses are prone to becoming unnerved when confined within a trailer and the surges and shocks can cause them to become even further unnerved and scared. A racehorse, for example, can become too xe2x80x9cstressed-outxe2x80x9d from having been transported in a trailer to perform at peak efficiency, and consequently, the horse""s owner may suffer financially. Thus, it is desirable to reduce the surges and shocks transmitted to the trailer for the comfort of the livestock and for the protection of other cargo that may be harmed by surges and shocks.
Trailer hitches are designed to accommodate various tongue weights of a trailer. Ideally, the tongue-weight is five to ten percent of the gross trailer weight. An excessive tongue weight, a tongue weight greater than the rated capacity of the trailer hitch, leads to undue wear and damage to the trailer hitch and to the towing vehicle, and is also a safety hazard. An excessive load placed on the trailer hitch results in the rear end of the towing vehicle being pushed downward, and the front end of the towing vehicle becoming raised. The raised front end reduces the contact load between the steering wheels of the towing vehicle and the road or ground, thereby creating a safety hazard for the operators of the towing vehicle and all other drivers sharing the road with the towing vehicle. Conversely, trailer tongues having a tongue weight of less than five percent of the trailer""s gross weight are prone to accidentally becoming decoupled from the trailer hitch; a bump in the road can result in an upward vertical shock greater than the load exerted by the tongue on the hitch ball. The net upward vertical force might result in the decoupling of the trailer from the trailer hitch. Thus, for safety reasons it is important to apply the correct tongue weight to the trailer hitch.
Therefore, there exists a need for a trailer hitch assembly that has the ability to dampen surges and shocks between the towing vehicle and trailer in both the longitudinal and vertical directions simultaneously. Furthermore, there exists a need for a hitch assembly that can measure the tongue weight of the trailer to make sure that the proper weight limit applied by the tongue of the trailer to the hitch ball is not exceeded.
Briefly described, the invention is directed to a hitching mechanism that dampens both surges and shocks experienced between a towing vehicle and its"" trailer. Vertical and longitudinal forces applied to the hitching mechanism are dampened by a torsional spring included in the hitching mechanism.
In one embodiment of the invention, a hitch assembly for coupling to a tongue of a trailer includes a draw bar having first and second opposed ends, a yieldable retaining means, and a means for mounting a tongue of a trailer. The first end of the draw bar is removably coupled to a receiver tube rigidly mounted to a towing vehicle. The trailer mounting means is pivotally supported at a pivot point on the draw bar and extends from the pivot point to a distal end having a means for receiving a hitch ball. The hitch ball receiving means is horizontally and vertically offset from the pivot point of the draw bar such that the mounting means moves in an arc about the pivot point in response to shocks and surges, i.e. horizontal and vertical forces, experienced between the towing vehicle and the trailer tongue. In response to the mounting means pivoting in an arc about the pivot point the yieldable retaining means provides a retaining force to resist the pivoting and to biases the mounting means to a predetermined position.
In another embodiment, the invention includes a conventional rectangular draw bar, a torsional spring assembly mounted to the draw bar at the pivot point, and a hitch ball assembly mounted to the torsional spring so that the draw bar is biased by the torsion spring about the pivot point toward a predetermined position. The hitch ball assembly includes a pair of opposed side load support arms, a spindle and a spacer-bar assembly that extend between the side arms. The draw bar is received by a receiver tube mounted rigidly to the towing vehicle, and is removably coupled thereto. The draw bar has a top wall with a housing of a torsional spring apparatus rigidly affixed thereto. Thus, when the draw bar is coupled to the receiver tube, the towing vehicle, the receiver tube, the draw bar and the torsional spring housing define a rigid structure that moves as one piece.
In accordance with one embodiment, the torsional spring apparatus includes a torsional housing which is transversely mounted to the top wall of the draw bar and has a generally square hollow elongated interior that extends normal to the length of the draw bar. A plurality of rubber cords are positioned at the comers of the square interior. A square spindle having opposed ends extends though the torsional housing. The square spindle is generally co-axially aligned with the center-line of the interior of the housing and held therein by the plurality of rubber cords. The plurality of rubber cords simultaneously abut the sides of the square spindle and the interior comers of the housing. The rubber cords essentially surround the square spindle urging the spindle toward a predetermined position.
In accordance with a preferred embodiment, a pair of generally reclined, or open, L-shaped, load bearing side arms are removably attached at one end thereof to the opposed ends of the square spindle. A spacer-bar assembly configured to receive a hitch ball is mounted between the load bearing support arms. The hitch ball assembly includes a spacer-bar, the load bearing side arms, and the spindle, and these elements pivot as one element about the center-line of the torsional housing. The hitch ball assembly is configured to receive the hitch ball such that the hitch ball is horizontally and vertically offset from the center-line of the torsional housing. Thus, the hitch ball assembly pivots in an arc about the center-line of the torsional housing in response to shocks and surges transmitted between the towing vehicle and the trailer. With this arrangement, forces transmitted between the towing vehicle and the trailer are dampened by the rubber cords as the cords resist the pivoting motion of the spindle.
In accordance with one embodiment of the invention, the torsional spring apparatus working in conjunction with the side arms form a spring scale for weighing the tongue weight of a trailer. On the top wall of the housing is a plurality of essentially parallel lines forming an incremental scale for indicating the load being applied to the spacer-bar assembly by a tongue of a trailer. The upper portion of one of the side arms has a notch cut out of it with a groove formed therein. When a load is applied to the spacer-bar assembly, the pair of side arms and the spindle pivot as one structure in response to the load. The pivoting of the spindle compresses the rubber cords between the spindle and the interior sidewalls of the housing and the compression of the rubber cords counters the torque applied to the spindle by the load. Thus, the displacement of the groove due to the pivoting of the side arms corresponds to the load being applied to the spacer-bar assembly, and the load is determined from the alignment of the groove with the incremental scale.
Thus, it is an object of the present invention to provide an improved trailer hitch whereby fore or aft surges and vertical shocks between the towing vehicle and its trailer are simultaneously absorbed or reduced.
Another object is to provide for an improved trailer hitch capable of simultaneously absorbing vertical shocks and fore or aft surges which is of simplistic design with a minimum number of components allowing for a lower manufacturing cost.
Still another object of the invention is to provide an improved trailer hitch with a load gauge capable of displaying the vertical load on the hitch.
Other objects, features and advantages of the present invention will become apparent upon reading the following specification which taken in conjunction with the accompanying drawings.